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Transmission Pan Leaking - What did I do?

Hi there ... hoping you all can help me out.

I have a 2006 Dodge Grand Caravan SE 3.3L with 90k miles on it.
I have done regular transmission pan and filter changes at 30k, 45k, and 60k with Ultra Black silicone and have had no leaks before this. However, since dropping and reinstalling the pan this time around at 90k, it's leaking out the rear (bottom) side of the pan, and I don't understand why.

Here is what I have done so far (at 90k miles):
1. Dropped the pan, removed the filter, and left to drip overnight
2. Used a wire wheel to remove all gasket material from pan and bottom of tranny. Left lots of very small scratches from the wires, and the black finish on the pan is completely gone, replaced by a very shiny steel surface with lots of tiny scratches (but no large gouges that I believe would cause leaks), and I've done this every time before.
3. Cleaned pan and transmission mating surfaces with WD-40, but can't remember if I did this before or not.
4. Applied 1/8" of Ultra Black to pan (yes, inside bolt holes), waited 15min for tackiness, and then stuck on pan.
5. Tightened bolts down a little more than finger tight, waited 1 hour, then torqued to 14 ft-lbs.

I'm thinking it might be one of two things: (1) my repeated wire brushing of the pan may have compromised its ability to seal, or (2) that the WD-40 must be preventing the Ultra Black from sealing correctly, as I read on another forum that you should only use brake cleaner to clean the mating surfaces.

Well, I'm wondering why do you change the tranny oil & filter so frequently at 15K to 30K intervals... Are you a heavy duty user who tows a lot? Is the oil and filter really dirty or worn out when you change them?

You like doing unnecessary work/maintenance?
I have good news for you, you get to drop the pan again and this time use brake parts cleaner or electric parts cleaner if former is unavailable (you can use benzene in a pinch) but both surfaces must be oil and grease free or that silicone has nothing to grab onto..

When you get tired of it, use a fluid extractor (vacuum) pump to replace just the fluid via dipstick or invest in a drain plug pan (hint: now is a good time to look for that doorman pan with a drain plug)

BTW, if you check your owner's manual you'll see that you only need to service the trans at 60,000 mile intervals, for vehicles with ATF+4 from the factory (if following severe duty schedule)...

I use paint thinner for this purpose and no problems. Change mine once a year which is 25 to 30k miles, I would call my driving extremely severe service (especially on the tranny) because I tow my work trailer almost daily.

Kudos to you for servicing your transmission! Fresh, clean fluid and a new filter will NEVER hurt your transmission!

As you can see from this heat chart, at 250 degrees fluid is good for about 25k miles... and in my '97 with a 30,000 GVW transmission cooler the temperature easily went up to 225 degrees in stop and go traffic. Without an auxillary cooler, I would imagine the temps are higher.